This invention relates in general to capillary devices and in particular to a capillary device useful in capillary electrophoresis and capillary chromatography.
Capillary zone electrophoresis (CZE) in small capillaries has proven useful as an efficient method for the separation of solutes. An electric field is applied between the two ends of a capillary tube into which an electrolyte containing the solutes is introduced. The electric field causes the electrolyte to flow through the tube. Some solutes will have higher electrokinetic mobilities than other solutes so that the solutes form zones in the capillary tube during the flow of the electrolytes through the capillary. To aid the analysis of the contents of the electrolyte or to aid the detection of such contents, fluids have been introduced in a second capillary connected to the main capillary through which the electrolyte flows. This causes the fluid introduced in the second capillary to mix with portions of the electrolyte in the main capillary to aid the analysis, detection or separation in the CZE process.
In order to introduce another fluid into the electrolyte in the main capillary, the main capillary has to be connected at a location between its two ends to a second capillary tube. One type of connection is formed by breaking the main capillary into two parts and connecting the two parts to a third tube through a T-shaped connector. This and other types of connectors for introducing another fluid to mix with the electrolyte are disadvantageous because they contain too much dead space at the connection between the two capillaries.
It is frequently desirable to detect compounds in the electrolyte occurring in very small quantities. For this reason, the CZE process is performed with very small capillaries to enhance the separation of such trace compounds from other constituents of the electrolyte. Such traces will be detected when certain peaks occur in electropherograms. When such trace compounds pass through the connection, the dead space at such connection will cause the trace compounds to be mixed with other constituents in the electrolyte; this has the effect of broadening the peaks in the electropherograms. This reduces the sensitivity of detection and resolution of traces of compounds and is therefore undesirable. It is therefore desirable to provide devices which permit a fluid to be introduced into the electrolyte during its flow in a CZE process in which the peak broadening effects are reduced.
In capillary chromatography, analysis and separation are achieved in a manner similar to the CZE process except that the fluid in the capillary is moved by pressure instead of by an electric field. For considerations similar to those described above, it is desirable to provide a capillary device which permits a second fluid to be introduced at any point in the flow of a first fluid through a main capillary in capillary chromatography where peak broadening effects are reduced.